¹Carine Sadaka, ¹Jérôme Gattacceca, ^1,2,3Florian Dumas, ¹Régis Braucher, ¹ASTER Team, ⁴Matthieu Gounelle, ⁵Dilyara Kuzina, ⁶Cyril Lorenz, ⁷Alexandre Corgne, ⁸Pierre Sempéré
Meteoritics & Planetary Science (in Press) Open Source Link to Article [DOI: 10.1111/maps.70219]
¹Aix-Marseille Univ, CNRS, IRD, INRAE, CEREGE, Aix-en-Provence, France
²Laboratoire G-Time, Université Libre de Bruxelles, Brussels, Belgium
³AMGC, Vrije Universiteit Brussel, Brussels, Belgium
⁴Institut de minéralogie, de physique des matériaux et de cosmochimie—UMR7590, Muséum National d’Histoire Naturelle, Paris, France
⁵Institute of Geology and Petroleum Technologies, Kazan Federal University, Kazan, Russia
⁶Vernadsky Institute of Geochemistry and Analytical Chemistry, Moscow, Russia
⁷Instituto de Ciencias de la Tierra, Universidad Austral de Chile, Valdivia, Chile
⁸Independent Contributor, Agen, France
Published by arrangement with John Wiley & Sons

We present a comprehensive study of a meteorite collection from the Atacama Desert (Chile), the driest and most climatically stable desert in the world. This collection includes meteorites from three adjacent Dense Collection Areas (DCAs) in the northern part of the Atacama Desert: Calama, Sierra Gorda, and Chug Chug, referred to as the “Calama area.” Within this region (~550 km²), we conducted a systematic search over a 2.5 km² zone in the Calama DCA and compared the resulting density to the nonsystematic recovery density in the Calama area. We also present the ³⁶Cl-based terrestrial ages of 49 ordinary chondrites selected from the Calama area. The systematic search yielded a meteorite recovery density of 38 meteorites per km² (15 meteorites per km² for meteorites >20 g), and the collection exhibits a median terrestrial age of 303 ka. Notably, compared with the El Médano and Catalina DCAs, the Calama area is characterized by a lower meteorite density and younger meteorite terrestrial ages, most likely reflecting the region’s more humid climate and more dynamic geomorphology due to its proximity to the pre-Andean range. Our results further show that meteorite weathering is not correlated with terrestrial age but is instead essentially controlled by the initial porosity of the meteorite, itself related to shock stage. Nevertheless, the Calama area still exhibits higher densities and older terrestrial ages than any other hot desert in the world, confirming that the long-term preservation of meteorites is observed across the entire Atacama Desert.

¹Ji-In Jung, ^1,2Sophia Gaal, ^1,3Sonia M. Tikoo, ¹Ethan Lopes, ¹Jonathan Mells, ³Dale H. Burns, ⁴Robert G. Hatfield
Meteoritics & Planetary Science (in Press) Link to Article [DOI: 10.1111/maps.70217]
¹Department of Geophysics, Stanford University, Stanford, California, USA
²Department of Geological Sciences, The University of Alabama, Tuscaloosa, Alabama, USA
³Department of Earth and Planetary Sciences, Stanford University, Stanford, California, USA
⁴Department of Geological Sciences, University of Florida, Gainesville, Florida, USA
Published by arrangement with John Wiley & Sons

Paleomagnetic investigations of pallasites are important for understanding the dynamo histories of their parent bodies and the formation mechanisms of these meteorites themselves. To understand the temporal evolution of pallasite parent-body dynamos, additional paleomagnetic studies of new meteorites are needed. However, such efforts require a thorough understanding of magnetic carriers and recording properties of pallasites to ensure that any observed remanence reflects primary magnetic records. Here, we investigate olivine grains in the main group Sericho pallasite to evaluate their suitability for paleomagnetic studies. Electron microscopy, combined with rock magnetic analyses, reveals colloidal, euhedral magnetite grains hosted within iron oxide veins (likely goethite) formed during post-fall aqueous alteration within our Sericho sample. All results indicate that secondary mineral phases dominate the remanence, precluding reliable recovery of primary parent-body magnetic fields. Our study presents a cautionary tale about how different samples of the same meteorite can experience heterogeneous degrees of weathering, ranging from effectively pristine to so altered that paleomagnetic studies probing parent body processes cannot be conducted. As such, meteorites must be carefully scrutinized on an individual-sample basis before paleomagnetic studies to ensure high-fidelity results.